Abstract: According to the theoretical analysis of the general formulas deter-mining the frequency response (P_a(F))/(N_e²P_ao)~F, it is proved that, underany circumstance, the condtion that the frequency response curves are symmetric about the central frequency F=1 is always F₁+F₂=2. Based upon this argument, we determine, through systematical calculations, the largest Bragg bandwith which can be obtained for various number of transducer pieces N_e. At the same time, we obtain the optimum design of acoustooptic devices.